
const fp = require("lodash/fp")

const { Maybe, Container } = require("./3.index.js")

// 实现一个函数ex2， 能够使用fp.first 获取列表的第一个元素
let xs = Container.of(["do", "ray", "me", "fa", "so", "la", "ti", "do"])
let ex2 = (x) => {
  return fp.first(x)
}
const first = xs.map(ex2)
console.log(first)